WORKSHEET
CLASS: 9
SUBJECT: CHEMISTRY
TOPIC: EMPERICAL FORMULA
Q1. A compound gave the following data: C = 57.82% , O = 38.58% and the rest hydrogen. Its vapour density is
83. Find its empirical and molecular formula. [C=12 , O = 16, H = 1].
Q2. Four g of a metallic chloride contains 1.89 g of the metal ‘X’. Calculate the empirical formula for the
metallic chloride. [At. Wt. Of ‘X’ = 64 , Cl = 35.5]
Q3. Calculate the molecular formula of a compound whose empirical formula is CH 2O and vapour density is 30.
Q4. A compound has the following percentage composition. Al = 0.2675g, P = 0.3505g; O = 0.682g. If the
molecular weight of the compounds is 122 and its original weight which on analysis gave the above results
1.30 g. Calculate the molecular formula of the compound. [Al = 27, P = 31, O = 16].
Q5. Two organic compounds ‘X’ and ‘Y’ containing carbon and hydrogen only have vapour densities 13 and 39
respectively. State the molecular formula of ‘X’ and ‘Y’. [C = 12, H = 1].
Q6. A compound has the following % composition. Zn = 22.65% ; S = 11.15%; O = 61.32% and H = 4.88%. Its
relative molecular mass is 287 g. Calculate its molecular formula assuming that all the hydrogen in the
compound is present in combination with oxygen as water of crystallization. [Z = 65,S = 32, O = 16, H = 1].
Q7. What is the empirical formula of octane. [C8H18]
Q8. A compound contains – Carbon 14.4% , hydrogen 1.2% and chlorine 84.5%. Determine the empirical
formula of this compound. Work correct to 1 decimal place. The relative molecular mass of
this compound is 168, so what is its molecular formula. [C = 12, H = 1, Cl = 35.5]
Q9. A gaseous compound of nitrogen and hydrogen contains 12.5% hydrogen of mass. Find the molecular
formula of the compound if its relative molecular mass is 37. [N = 14, H = 1].
Q10. An organic compound has vapour density 94. It contains C = 12.67% , H = 2.13% and Br = 85.11%. Find
the molecular formula of the organic compound. [C = 12, h = 1, Br = 80].
Q11. A compound having empirical formula X2Y is made of two elements X and Y. Find its molecular formula if
the atomic weight of X is 10 and that of Y is 5 and the compound has a vapour density 25.
Q12. Find the empirical formula of a compound containing 17.64% hydrogen and 82.35% nitrogen.
[At. wts. N = 14, H = 1]
Q13. On analysis a substance was found to contain:C = 54.54% , H = 9.09%, O = 36.36%.
The vapour density of substance is 44. Calculate: empirical formula and molecular formula.
[At. wt. C = 12, H = 1, O = 16]
Q14. Find the empirical and molecular formula of an organic compound from the data given below:
C = 75.92%, H = 6.32%, N = 17.76% [At wts. C = 12, H = 1, N = 14]
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